“Oh, it’s you,” said Ron, looking at Malfoy as if he were something unpleasant on the sole of his shoe. “Bet you’re surprised to see Harry here, eh?”
“Not as surprised as I am to see you in a shop, Weasley,” retorted Malfoy. “I suppose your parents will go hungry for a month to pay for all those.”

Harry Potter and the Chamber of Secrets - Chapter 4 : At Flourish and Blotts
See this quote in the Pensive -